1. Field of the Invention
This invention relates to the field of Radio Frequency Identification (RFID) tags and labels, and in particular to tags and labels that include an antenna structure.
2. Description of the Related Art
Current inventory and manufacturing methods rely on the ability to track and identify items of concern, such as inventory items, packages, individual parts, etc., and to communicate information concerning such items of concern in a wireless manner for processing and use. One known method of tracking and providing information on such items of concern is to attach to each such item a wireless communication device, such as an active or passive transponder, incorporated into an identification tag or label that responds to radio frequency interrogation and commands. The tag may store or represent information concerning the object to which it is attached, such as a unique identifying number, object status such as opened or unopened, location, and the like. The tag may be attached to an individual item or to packaging containing multiple items.
One example of a prior art RFID device 1 is illustrated in FIG. 1. The device 1 includes a chip 2 coupled to a simple dipole antenna structure 3. The antenna structure 3 consists of a pair of antenna elements 4 and 5 on a substrate 6.
One difficulty with the simple dipole antenna structure 3 illustrated in FIG. 1 is that the readability of the structure may be highly dependent on its orientation. For instance, readability of the device 1 along its edges, especially parallel to the direction of the antenna elements 4 and 5, along a narrow axis 8 of the device 1, may be difficult.
It will be appreciated that it would be desirable to have RFID devices that overcome the previously-mentioned difficulties.